1. Field of the Invention
This invention relates to a method to erase data stored on an optical recording medium and, more particularly, to a method to erase data stored on a blu-ray disc by indexing an infrared-light laser one track every 0.4 revolutions of the disc.
2. Description Of Background
An optical recording medium records and reproduces data by using a laser beam. Blu-ray Disc (BD) for example, is an optical disc format meant for storage of high-definition video and high-density data. A single-layer BD can store enough for approximately four hours of high-definition video with audio. A dual-layer BD can hold enough for approximately eight hours of High Definition (HD) video. Capacities of 100 GB and 200 GB, using four and eight layers respectively, are currently being researched. Blu-ray systems use a blue-light laser operating at a wavelength of 405 nm, similar to the one used for High Definition Digital Versatile Disk (HD-DVD), to read and write data. DVDs and CDs use red-light and infrared-light lasers at 650 nm and 780 nm respectively.
A bulk erase has been used for performing a polarization or an initialization and a sensitivity shift of the optical recording medium. For example, a semiconductor laser for a DVD drive may have a peak beam power of approximately 150 milliwatts (mW) and the beam makes a mark on the media along the tangential direction of varying lengths, this mark having a diametral axis of approximately 0.4 μm in the radial direction of a disc. The rotating disc is irradiated with the laser beam by focusing only on the recording film to raise the temperature of the recording film. Erasing DVD, and hence Blu-Ray, currently requires that each track be erased with the same laser beam used to write the information, a process which only allows one track to be erased at a time, or one track per revolution of the disk. However, there is a need for a faster and economic erase method of an optical recording medium, namely one which erases an entire track for a fraction of a revolution of the disk.